$1500 is nothing if you're a telco. If cost were the reason they wouldn't blink at having five caesium fountains in each location - but as another observed it's

$1500 is nothing if you're a telco. If cost were the reason they wouldn't blink at having five caesium fountains in each location - but as another observed it's likely about synchronicity - relativity is a problem if you're looking to have two clocks on opposite sides of the planet in perfect sync.